rdesktop is an open source client for Windows NT Terminal
Server and Windows 2000 Terminal Services, capable of
natively speaking Remote Desktop Protocol (RDP) in order
to present the user's NT desktop. Unlike Citrix ICA, no
server extensions are required.
rdesktop currently runs on most UNIX based platforms with
the X Window System, and other ports should be fairly
straightforward.
rdesktop is used through rfbdrake.